Quimiotaxonomia de insetos necrófagos Calliphoridae, Muscidae, Sarcophagidae e Stratiomyidae (Diptera) de potencial forense utilizando perfis de hidrocarbonetos cuticulares

Abstract

The chemotaxonomy based on cuticular hydrocarbon profiles (CHs) is a taxonomic tool that has been used for insects since the 1970's and their use is based on the species-specificity. In Diptera, significant studies have been published showing that CHs can be used in chemotaxonomy, being useful even for distinction of cryptic species. The Sarcophagidae family include species of forensic importance, which are pioneers in cadaveric degradation and those of genres Peckia Robineau-Desvoidy, 1830 and Oxysarcodexia Townsend, 1917 are often found in animal carcasses and human corpses. This study aimed to describe, by gas chromatography coupled tomass spectrometry (GC-MS), the profiles of the CHs of adults from nine species of the family Sarcophagidae, considering gender and geographical distribution, and compare the resulting profiles with the other species of the families Calliphoridae, Muscidae and Stratiomyidae. The extraction of CHs were made in triplicate using ten female and/or ten males for every species collected in the field. The methodology used for the extraction and analysis followed previously described protocol. We used the GC-MS from the Laboratório de Toxicologia of the Fundação Oswaldo Cruz. Only the CHs with chain length ranging from 21 to 40 carbons were identified, since these are the most commonly found in insects. The relative abundance of each peak was obtained by calculating its area in relation to the total area of the sample, and only those with more than 0.5% were identified. Altogether, 213 compounds were identified and classified as n-alkanes, methyl-branched alkanes and alkenes ranging from 22 to 39 carbons in the main chain (CMC). In Sarcophagidae 164 compounds were identified ranging from 22 to 39 CMC and each species had a different number of identified CHs. Oxysarcodexia thornax was the species with the largest number of identified CHs (48 compounds), contrasting with Peckia (Squamatodes) ingens with the fewest (26 compounds). All species of Sarcophagidae presented specific HCs, as Malacophagomyia filamenta, which was the only that presented trimethylalkanes in its profile as well as having the largest number of specific CHs (14), while Oxysarcodexia intona had the lowest amount (2). Some species show sexual dimorphism, as Ravinia belforti, whose males presented 41 and females 32 HCs with more than 0.5% of abundance. The populations of O. thornax from different regions of Brazil showed similar chromatograms, but, as expected, there were fluctuations in the abundance of shared CHs and only a few specific per population. The two dendrograms generated to assess the similarity among the HCs profiles of the species resulted in different relationships. When n-alkanes are taken into account, the dendrogram showed good correlation among the species of Sarcophagidae, but not among Calliphoridae and Muscidae. However, when excluding the n-alkanes from the analysis, the species of Sarcophagidae continued with good correlation, the Calliphoridae and Muscidae were better correlated and Stratiomyidae, as expected, was presented as the most dissimilar species. The results showed promising use of this technique for the identification of species from Sarcophagidae,and other forensic important families , making it possible to establish a chemotaxonomic database of these species.